1. Field of the Invention
The present invention relates to a security locking device for a gladhand air brake system for a truck trailer.
2. Description of the Prior Art
Modern day truck trailers are equipped with air actuated brake systems which typically rely on compressed air supplied from the tractor. Consequently, when the trailer is disengaged from the truck, the brakes remain in their locked position thus securing the trailer against movement.
By current practices, loaded trailers are frequently left unattended, either in a staging or storage area or even at a scheduling stop. Such trailers are often loaded with extremely valuable cargo thus raising the temptation for theft when left unattended.
The mechanical hitching together of a truck tractor to a trailer is typically achieved by what is sometimes referred to as a fifth wheel for the mechanical connection and then air hoses are coupled together to supply compressed air to the trailer brake system for the purposes of operation thereof. These coupling devices are typically referred to in the trade as gladhand couplers. Such coupling devices have more or less of a general overall universal design such that numerous different trucks may be utilized to haul different trailers.
The unauthorized taking of a trailer loaded with cargo is facilitated by the fact that a tractor may be readily and quickly backed up and hitched to a trailer, the gladhand couplers coupled together and the brakes thereof released to ready the trailer for operation. Thus, unauthorized persons may surreptitiously tow away an unattended trailer and unload and dispose of the cargo before the whereabouts of that trailer may be traced by the authorities. Consequently, there exists a need for a security mechanism which will secure a gladhand trailer coupler against unauthorized mating with a trailer coupler. This need has led to proposal of several different designs.
One such device proposes the use of a lock cylinder insertable directly into the opening for the air passage to block access thereto. The cylinder then incorporates radially extendable locking fingers which extend to lock the cylinder in place. A device of this type is shown in Menzie U.S. Pat. No. 4,325,327. Devices of this type, while serving to block access, suffer the shortcoming that the cylinder lock is intrusive in that it creates a danger of causing damage to the seal and, further, is limited in application to different sizes and configurations of seals and does not form a sealing engagement therewith to prevent entry of debris.
Another such prior art coupling device takes advantage of the fact that the gladhand includes a generally cylindrical housing formed with a central air passage and having a tongue projecting from one side thereof and a crown mounted on the opposite side thereof and turned upwardly and backwardly to form a cap. The security lock itself is formed on one side with a so-called tongue for receipt under the cap and on the other side with a down turned flange formed with a horizontally extending slot which is in intended for receipt of the aforementioned coupling tongue. A lock cylinder is then mounted centrally in the body of the security lock and is arranged such that the security lock itself may be slid bodily in a diametrical direction to engage the opposite side thereof with the coupler housing and allow for the lock plunger to be extended into the air passage.
A device of this type is shown in Strickland U.S. Pat. No. 4,226,103. Such an arrangement, while satisfactory for some applications, suffer the shortcoming that the security lock is difficult to install and the lock plunger intrudes directly into the air passage, thus limiting the universality of the security lock and presenting a danger that such plunger might do damage to the air passage. Moreover, in order to allow for installation of this device, the tolerances must be relatively loose thus resulting in the security lock itself being relatively loose upon installation thereof thereby leaving a substantial degree of looseness between the components resulting in a space being left into which pry tools or the like may be inserted. Of greater importance is the fact that such devices do not provide a positive seal to block entry to the air passage thus leaving an unsealed opening for entry of debris which tends to clog filters or otherwise contaminate the brake system.